Curing and Alignment of Liquid Crystalline Epoxy Networks

1990 ◽  
Vol 203 ◽  
Author(s):  
C. K. Ober ◽  
G. G. Barclay ◽  
K I. Papathomas ◽  
D. W. Wang
Keyword(s):  
Liquid Crystalline ◽  
Coefficient Of Thermal Expansion ◽  
Wide Angle ◽  
Curing Process ◽  
X Ray Diffraction ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
X Ray ◽  
Epoxy Networks ◽  
Liquid Crystalline Epoxy

ABSTRACTLiquid crystalline epoxy networks have been prepared from glycidyl terminated polyether oligomers of varying molecular weight. These oligomers were prepared by functionalizing hydroxy terminated oligomers based on 4,4'- dihydroxy-α-methylstilbene and α,ω-dibromoalkanes with glycidyl groups. Curing of these oligomers was carried out either within their nematic mesophase or in their isotropic state. Different thermal properties were observed after curing under these two sets of conditions. Extremely low values of the coefficient of thermal expansion in the range of 15 to 60 ppm/°C were achieved. To produce aligned thermosets, orientation of the liquid crystalline phase was induced during the curing process by a magnetic field. Orientation of these networks was measured by wide angle x-ray diffraction (WAXD).

Effect of Processing Variables on The Magnetic Field Orientation of Liquid Crystalline Thermosets

1999 ◽  
Vol 559 ◽  
Author(s):  
Derek M. Lincoln ◽  
Elliot P. Douglas
Keyword(s):  
Magnetic Field ◽  
Liquid Crystalline ◽  
Fractional Factorial Design ◽  
Fractional Factorial ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Liquid Crystalline Epoxy ◽  
Processing Variables ◽  
Degree Of Orientation ◽  
The Magnetic Field

ABSTRACTWe have investigated the effect of various processing variables on the magnetic field orientation of a liquid crystalline epoxy. By using a modified fractional factorial design, we created an empirical model which can be used to predict the degree of orientation as a function of these variables. The model predicts the correct qualitative trends, namely that orientation increases with increasing magnetic field strength, increases with increasing time in the field, and decreases with increasing B-staging. The model also reveals some surprising effects of B-staging on the degree of orientation.

Liquid Crystalline Thermosets As Materials For Microelectronics

1991 ◽  
Vol 227 ◽  
Author(s):  
C. K Ober ◽  
G. G. Barclay
Keyword(s):  
Thermal Expansion ◽  
Liquid Crystalline ◽  
Coefficient Of Thermal Expansion ◽  
High Thermal Stability ◽  
Isotropic Phase ◽  
X Ray Diffraction ◽  
Primary Interest ◽  
Functional Monomers ◽  
X Ray ◽  
Orientation Parameters

ABSTRACTNew liquid crystalline thermosets have been prepared from end-functional monomers and oligomers of varying molecular weight. Both triazine and epoxy networks were explored. Of primary interest was the exploitation of the mesophase properties of these networks for developing polymers with high thermal stability and low coefficients of thermal expansion (CTE). Curing was carried out either within the nematic mesophase or the isotropic phase of the prepolymers. Transition temperatures associated with the mesophase were observed to change after curing under these two sets of conditions. The networks with the highest crosslink density were found to exhibit the lowest CTE values. Crosslinking of these thermosets was also carried out in the presence of a 13.5 Tesla magnetic field to determine the effect of orienting fields on the curing of the LC network. Orientation parameters as measured by wide angle x-ray diffraction were as high as 0.6. Values of the coefficient of thermal expansion as low as 15 ppm were achieved in the aligned direction. Of the two resin types, those with the triazine crosslinks had the lowest thermal expansion coefficient. Other thermal properties of these networks will be discussed.

Phase Transitions In Blends Of Liquid Crystalline Polymer/Polyether Imide

1991 ◽  
Vol 227 ◽  
Author(s):  
Joonhyun Nam ◽  
Tomohiro Fukai ◽  
Thein Kyu
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Single Phase ◽  
Crystalline Polymer ◽  
Recrystallization Process ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Time Resolved ◽  
X Ray

ABSTRACTA thermotropic liquid crystalline copolymer consisting of bisphenol E diacetate, isophthalic acid and 2,6-naphthalene dicarboxylic acid was blended with polyether imide by dissolving in a mixed solvent of phenol/1,1,2,2-tetrachloroethane in a ratio of 60/40 w/w and co-precipitating the ternary solution in non-solvent (methanol). Wide-angle x-ray diffraction and differential scanning calorimetry studies revealed that the blends were completely amorphous with a single glass transition temperature. The single phase was probably entrapped during solvent removal, but these mixes were unstable and phase separated upon heating. Mesophase structure developed in the LCP rich region with continued annealing. The evolution of crystalline texture was monitored by time-resolved wide-angle x-ray diffraction following a temperature jump from ambient to 265 °C. The recrystallization process of LCP was found to slow down in the blend state relative to that of the neat LCP.

Magnetic Field Orientation of Liquid Crystalline Epoxy Thermosets

1998 ◽  
Vol 31 (15) ◽  
pp. 4730-4738 ◽  
Author(s):  
Brian C. Benicewicz ◽  
Mark E. Smith ◽  
Jim D. Earls ◽  
Ralph D. Priester ◽  
Stefan M. Setz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Liquid Crystalline ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Liquid Crystalline Epoxy

Synthesis and Properties of Liquid Crystalline Polyurethanes from 4,4-bis (6-hydroxyhexoxy) Biphenyl and 3,3'-Dimethyl-4, 4’-Biphenylene Diisocyanate

2010 ◽  
Vol 428-429 ◽  
pp. 144-149
Author(s):  
Xiao Dong Chen ◽  
Nan Qiao Zhou ◽  
Hai Zhang
Keyword(s):  
Nematic Phase ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Decomposition Temperature ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Temperature Range

A thermotropic liquid crystalline polyurethane (LCPU) was synthesized by the polyaddition reaction of 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI) with 4,4-bis(6-hydroxyhexoxy)biphenyl (BHHBP). The liquid crystalline behavior of the polymer was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide angle X-ray diffraction (WAXD). The LCPU exhibited a nematic phase with a threaded texture and had a wide mesophase temperature range. And thermogravimetric analysis (TGA) indicated the decomposition temperature of the LCPU was >300°C. The observation of POM showed that the LCPU was a thermotropic nematic liquid crystalline polymer at certain temperature range.

Time-resolved small-angle X-ray scattering and wide-angle X-ray diffraction studies on the nanostructure of melt-processable molecular composites

2003 ◽  
Vol 36 (4) ◽  
pp. 986-990 ◽  
Author(s):  
Jaroslaw Janicki
Keyword(s):  
Small Angle ◽  
Liquid Crystalline ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
X Ray Scattering ◽  
Molecular Composites ◽  
Rigid Rod ◽  
Ray Scattering

Novel melt-processable molecular composites were obtained from isotactic polypropylene (iPP) and liquid-crystalline oligoester (LCO). The nanostructure and thermal behaviour of molecular composites were examined by real-time synchrotron small-angle X-ray scattering and wide-angle X-ray diffraction methods, and differential scanning calorimetry. The synthesized oligoester, with low melting temperature (391 K), exhibits the ability to form a thermotropic mesophase. It was shown that strong rigid rod-like macromolecules of LCO are dispersed at the molecular scale in iPP matrix and act as reinforcing fibres.

A quantitative differentiation method for plastic bags by wide angle X-ray diffraction for tracing the source of illegal drugs

2007 ◽  
Vol 168 (1) ◽  
pp. 37-41 ◽  
Author(s):  
Valerio Causin ◽  
Carla Marega ◽  
Pietro Carresi ◽  
Sergio Schiavone ◽  
Antonio Marigo
Keyword(s):  
Illegal Drugs ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Differentiation Method ◽  
Plastic Bags
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